Macroevolution is the set of long-term processes that contribute to the way life on our planet evolves as a whole. There are six important themes that are involved with macroevolution. Two of them are adaptive radiation and extinction.

Adaptive radiation is the process by which one species becomes many different species. This may happen because the species is split up into smaller groups that face different environments or because there are different opportunities for the species to evolve in many different ways, perhaps because of the availability of new resources. For example, Darwin’s finches started out as one species that immigrated to the Galapagos Islands from the mainland. Over time, they adapted to many different environments and roles in the ecosystem of the islands and evolved into many different species.

Extinction removes a species from the planet. This may be because of changing climate or resources, such as when the woolly mammoths went extinct when the ice ages that they were adapted for ended, or because they are not as well adapted as their competition. This opens up new resources and roles for other species to expand and possibly evolve to fill the empty niche left by the extinct species.

Mass extinctions have played an important role in the evolution of life on our planet. They have removed many species and made way for other species to expand and evolve further.

Mass extinctions have occurred many times in the Earth’s history and in some cases have killed off nearly all life on the planet. After each mass extinction, many types of organisms disappeared and never reappeared. Other species that did not play an important role in most ecosystems before the extinction now had ample space and resources to grow, multiply, and eventually expand to take up many new roles in the ecosystem. This expansion of roles often led to these species specializing in different roles and evolving new traits to adapt to those roles, ultimately leading to evolution of new species. Without mass extinctions, the world might be currently ruled by massive sea scorpions and other arthropods, or by dinosaurs, and mammals might still be tiny creatures that never evolved to take a major place in the world.

Convergent evolution occurs when two species from different lineages evolve very similar features. Usually this is because they are adapting to the same environment and similar features give them an advantage, no matter how they came to develop them.

A dolphin and a shark look very similar. Both have long, streamlined bodies, dorsal fins, and paddle-shaped fins to guide them through the water, as well as a long, muscular tail that propels them through the water. However, these animals are extremely distantly related. Dolphins actually evolved from land animals, in fact. So the development of similar features that adapts them to living in the marine environment is an example of convergent evolution.

The hox gene is master control gene that controls major characteristics of the organism that can give rise to different variation of the same organism.

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Gradualism and punctuated equilibrium are two theories of evolution. Both hypothesize that evolution occurs because of natural selection and is driven by environmental pressures, but they differ in how quickly evolution takes place. Gradualism states that evolution is a slow and steady process during which changes slowly accumulate in a species until it becomes a different species. Punctuated equilibrium states that evolution occurs in quick, short, bursts with long periods of stability (little or no change in the species) in between.

Convergent evolution states that throughout the years, tiny changes occur one after another in a species s that it slowly becomes a new species. It is like taking a cup of blue paint and slowly adding a few drops of yellow paint every few minutes until a while later you get green paint. The color changed slowly and gradually. Punctuated equilibrium, on the other hand, would be more comparable to using blue paint for an hour, then suddenly deciding you need green paint to continue with your painting, and dumping a ton of yellow paint in all at once to create green paint very quickly. In both cases you end up with the same result, but the process occurs at different rates.